Contour Enthusiasts Group Archives Forums Modifications Transaxle Fidanza Question

Any time acceleration is involved (which requires power), will show the benefits of the lighter flywheel; less power consumed to overcome the moment of interia of a lighter flywheel.

Although as you go up through the gears, it is less noticable...


So as you punch it on the dyno it should show up as an increase, but the increase would be different if you compared a 3rd gear pull to a 4th gear pull.

Actually, a lighter flywheel will make it easier to accelerate. This is the same concept as lightweight wheels. The reduction of rotating mass causes a lower rotational moment of inertia. Essentially it requires less force to accelerate something that weighs less.

The disadvantage of a lightweight clutch or wheel for that matter is that it is also that it is easier to accelerate.

The same property that makes it easier to accelerate to a higher speed makes it harder to remain at the same high speed. The flywheel has less momentum and since the engine and tires and whatnot are still producing the same amount of friction, the flywheel cannot use its rotating mass to keep the engine turning as easily.

The disadvantage of having a lightweight flywheel can most easily be seen when you are cruising along and come to a hill. With a very heavy flywheel, the rotational momentum helps keep the engine rotating at a constant speed (it wants to remain at a constant velocity), whereas with a light flywheel, the added force opposing foreward travel can slow the car down easier because there is not as much rotational momentum keeping the engine turning.

So yeah, that's that. This is all basic physics guys, don't let it fool you.

So you are saying that a lighter flywheel will get a car rolling from a dead stop faster.
You really can't believe that right???

A ligher flywheel has less stored inertia to start the transmission/wheels moving. This is that simple physics you mentioned!

It's also one of the reasons drag racers often use a heavier flywheel.

BTW - how would lighter wheels transfer less energy from the engine to the transmission? (I definitely see what mean, but it's not really the same comparison as you make it)

Greg,
There is no way on earth that a track racer would INCREASE the mass of the flyweel. The increase in mass directly relates to an increase in the moment of inertia and "simple physics" tells you that more enrgy is required to accelerate something with a higher moment of inertia.
E=(mv^2)/2 + (Iw^2)/2

Where:
E Energy
m mass of the body
v straight line velocity
I inertia
w angular velocity

So you can see that the ergergy required to accelerate an object is directly proportional to the moment of inertia. So something with a smaller mass and moment of inertia require less energy to accelerate it. hence why drag racers strip down the weight of there cars and reduce the mass of all rotating parts e.g. wheels, valavetrain, flywheel etc.

You can't argue with it....

And on a side note semi trucks have HUGE flywheels to help them maintain velocity while cruising and to help them take off from a dead stop because there mass is so huge that a light fllywheel would make it extremely hard for them to maintain the engine revs and keep their engines in the "power band". But the drawback is that is take a long time to rev up the engine in the first placer as it has to overcome the mass of the flywheel.

It may be okay to use a heavy flywheel for drag racing, but that is ONLY if you can launch by revving and holding the engine to a fixed rpm (usually with the use of a stutterbox) and then just feathering out the clutch. This is not nice for the clutch, and who has a stutterbox on a Contour?

Afterall, you are one of the biggest proponents on this board when it comes to arguing that the Conbtour is not a drag car, but a master of the twistied and the auto-x track.

So Demon, are you saying that thousands upon thousands of track racers use lightened flywheels for no reason NOT! They use it for one reason only, acceleration from a dead stop! better times! Are you about to tell me they spend all that time to add a lightened flywheel to go slower



hmmmm

When you say track are you talking autocross or drag racing???

I specifically stated drag racing.

Of course any autocross/road racer would use a lighter flywheel.

Also none of you have told me EXACTLY WHY you think what I stated is incorrect.

Heavier weight = more stored inertia (kinetic energy) = easier/faster acceleration from a DEAD stop. This is the ONLY point I state a heavier flywheel has an advantage (I seem to remember stating that at least 3 or 4 times now)

Stazi - In your last post you even agree with me;
"It may be okay to use a heavy flywheel for drag racing, but that is ONLY if you can launch by revving and holding the engine to a fixed rpm (usually with the use of a stutterbox) and then just feathering out the clutch. This is not nice for the clutch, and who has a stutterbox on a Contour?"

If you agree WTF is all this argueing about???

I don't ever recall saying a heavier flywheel was always better then a lighter one. I don't ever recall not endorsing or wanting a lighter flywheel.
I gave an accurate comparison of a lighter vs a heavier flywheel and people just see the "ONLY" time I said a heavier flywheel was better and some how correlate that to me stating heavier is ALWAYS better...

Sheesh people. READ all the posts in the thread before you jump off all half cocked...

drag racing

I still don't see how a heavier flywheel can improve dead-stop acceleration. Yes a lighter flywheel's lower rotational mass makes clutch engagement trickier from a stop, but the power to get you off the line isn't coming from "stored energy" in the flywheel, it's coming from the engine that the flywheel is connected to.